(a) Field of the Invention
The present invention relates to a clutch driven plate which may be mainly used in a dry clutch by riveting or bonding it to a clutch disc and to a method of producing the clutch driven plate.
(b) Description of the Related Art
In the conventional method of producing clutch driven plates for automobiles, a woven clutch driven plate has been produced by impregnating a fiber base material consisting of a long fiber, such as asbestos or glass fiber, with a thermosetting resin, rubber material, and other additives including friction modifier, etc., preforming the impregnated fiber base material by winding it into a torus form, thermo-compression molding the obtained torus body, and subjecting the molded product to finishing including after-curing, deflashing, abrasion, etc.
Also, as disclosed in Japanese Patent Application Kokai Koho (Laid-open) No. 61-41022 and Japanese Patent Application Kokai Koho (Laid-open) No. 61-70225, there has been known a method of producing a clutch driven plate which method comprises putting a resin-mold clutch facing plate composed of a non-woven fabric of asbestos, a thermosetting resin, and a friction modifier on a back-up plate made of a light metal such as aluminum, dulalumin, magnesium, etc., and thermo-compression molding the clutch facing plate and the back-up plate into one body. This method of producing a clutch driven plate does not include the step of impregnating a fiber base material with a bonding material and a friction modifier nor the step of preforming a tablet by winding, and therefore, this method saves time and processing fees in comparison with the method of producing a woven clutch driven plate. Further, the clutch driven plate produced by this method is generally more stable in quality than the woven clutch driven plate, and it has a higher breaking revolution speed because the back-up plate reinforces its strength.
The clutch driven plate produced by the above-described method, however, has a problem in that warping of the clutch driven plate is unavoidable because of the difference in thermal expansion coefficient between the back-up plate and the clutch facing plate and because of the curing shrinkage of the binder in the clutch facing plate.
The warped clutch driven plate has caused some inconveniences such that the rivet holes in the clutch driven plate and in a cushion spring of a dry clutch do not meet each other at the time of riveting, and that when the dry clutch employing the clutch driven plate is operated, only a part of the clutch facing plate contacts flywheel, resulting in uneven abrasion of the clutch facing plate.
Further, the clutch driven plate produced by the above method is heavier than the woven clutch driven plate, and its use in a clutch disc has caused the necessity for reinforcement of the synchro device of transmission gear.
In addition, there is another problem that because the back-up plate used for the clutch driven plate generally has a larger gravity than the clutch facing plate, the weight of the clutch driven disc is consequently increased. It results in an increase of the inertia of the clutch driven plate, and rotating the clutch driven plate inevitably requires a larger horsepower of engines.
As disclosed in Japanese Patent Application Kokai Koho (Laid-open) No. 61-256031, there has been known a clutch driven plate produced by integrally molding a center plate and a clutch facing constructed from a tape-like material and forming grooves on the surface of the clutch facing at the time of the integral molding.
The grooves formed in the above-described clutch driven plate are provided in order to exhaust the abrasion powder produced on friction thereby improving the friction efficiency. Therefore, each groove extends to both outward and inward peripheral edges of the clutch facing, and the clutch facing plate is divided by the grooves into sections. In case where the groove is deepened to make the clutch disc lighter and to reduce warp, there occurs the inconvenience that some parts of the divided clutch facing plate peel from the back-up plate, particularly, when the clutch driven plate and the flywheel do not engage uniformly against each other.